This invention relates to a method for mechanically protective production of finely dispersed micro-/nanoemulsions with a narrow droplet size distribution.
The invention also relates to a device for implementing the method.
The preparation of finely dispersed emulsions is an important development objective for the food, pharmaceutical, cosmetics, and chemical industries. The reason for this is the ability to keep such emulsions stable against settling with sufficiently small dispersed droplets, and to utilize the extremely large internal interface for the adsorption of functional ingredients (for example drugs, perfumes, pigments, etc.). The dispersed droplets also permit the buildup of particle networks that selectively influence the rheological properties of such emulsions.
Membrane emulsification methods are a new field for the manufacturers of machines and apparatus. Rotor/stator dispersing systems and high-pressure homogenization are ordinarily used for fine emulsification. Droplet dispersion in these apparatuses occurs under extremely high mechanical stress on both the dispersed and continuous phases. The membrane emulsification methods that have existed for about five years are very protective from the mechanical viewpoint compared to the conventional methods mentioned above, since the finely dispersed emulsion droplets are not produced by breaking apart larger drops, but are formed and released in their final size at the discharge orifices of the membrane pores.
In continuous membrane processes existing up to now, the continuous emulsion liquid phase flows tangentially over the membrane in the form of a pure shear flow. The shear stresses acting on the drops and detaching them from the membrane are not very efficient or not at all efficient with regard to detaching small drops and further dispersing (splitting) them, especially in case of high drop viscosities. This represents a considerable drawback with regard to the ability to adjust for small drop sizes and narrow droplet size distributions with the output capacities generally prescribed within narrow limits in the industrial production of emulsion systems.